Optimization of the Chin Bar of a Composite-Shell Helmet to Mitigate the Upper Neck Force (original) (raw)
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Finite element analysis of impact damage response of composite motorcycle safety helmets
Composites Part B: Engineering, 2002
The energy absorption during impact provided by a motorcycle safety helmet is always of critical importance in order to protect the rider against head injury during an accident. In the present study, a parametric analysis has been performed in order to investigate the effect of the composite shell stiffness and the damage development during impact, on the dynamic response of a composite motorcycle safety helmet. This kind of parametric analysis may be used as a tool during helmet design for minimising testing needs.
Materials & Design, 2012
In this study a new method for enhancing helmet performances during an impact is considered. In a first step an approved composite helmet finite element model is coupled with an anatomical head finite element model and is evaluated in terms of injury risks (risks of neurological injuries or subdural haematoma) under normative impact conditions (ECE 22.05 standard). Results show that the risk of head injuries is very high even if the considered helmet passes the standard. Thus a second step consists in proposing a new method for improving the helmet behaviour in case of impact by focusing on the outer shell characteristics and by assessing the head injury risk with the human head finite element model. A modal analysis of the entire helmet model is performed and makes it possible to define areas of the outer shell to be modified. Under standard impact conditions this new virtual helmet model conduces to a huge decrease of the head injury risk, both in terms of neurological injuries as well as in terms of subdural haematoma.
Effect of different helmet shell configurations on the protection against head trauma
The Journal of Strain Analysis for Engineering Design, 2019
Head trauma following a ballistic impact in a helmeted head is assessed in this work by means of finite element models. Both the helmet and the head models employed were validated against experimental high-rate impact tests in a previous work. Four different composite ply configurations were tested on the helmet shell, and the energy absorption and the injury outcome resulting from a high-speed impact with full metal jacket bullets were computed. Results reveal that hybrid aramid–polyethylene configurations do not prevent bullet penetration at high velocities, while 16-layer aramid configurations are superior in dissipating the energy absorbed from the impact. The fabric orientation of these laminates proved to be determinant for the injury outcome, as maintaining the same orientations for all the layers led to basilar skull fractures (dangerous), while alternating orientation of the adjacent plies resulted in an undamaged skull. To the authors knowledge, no previous work in the lit...
Relevant factors in the design of composite ballistic helmets
Composite Structures, 2018
In this paper, the design methodology of composite ballistic helmets has been enhanced considering biomechanical requirements by means of finite element analysis. Modern combat helmets lead to a new type of non-penetrating injury, the Behind Helmet Blunt Trauma (BHBT), generated by the deformation of the inner face of the helmet, the so-called backface deformation (BFD). Current standard testing methodologies use BFD as the main measure in ballistic testing. Nonetheless, this work discusses the relationship between this mechanical parameter and the head trauma (BHBT) by studying different head injury criteria. A numerical model consisting of a helmet and a human head is developed and validated with experimental data from literature. The consequences of non-penetrating high-speed ballistic impacts upon the human head protected by an aramid combat helmet are analysed, concluding that the existing testing methodologies fail to predict many types of head injuries. The influence of other parameters like bullet velocity or head dimensions is analysed. Usually, a single-sized helmet shell is manufactured and the different sizes are adjusted by varying the foam pad thickness. However, one of the conclusions of this work is that pad thickness is critical to avoid BHBT and must be considered in the design process.
Evaluation of head response to ballistic helmet impacts using the finite element method
International Journal of Impact Engineering, 2007
Injuries to the head caused by ballistic impacts are not well understood. Ballistic helmets provide good protection, but still, injuries to both the skull and brain occur. Today there is a lack of relevant test procedure to evaluate the efficiency of a ballistic helmet. The purpose of this project was (1) to study how different helmet shell stiffness affects the load levels in the human head during an impact, and (2) to study how different impact angles affects the load levels in the human head. A detailed finite element (FE) model of the human head, in combination with an FE model of a ballistic helmet (the US Personal Armour System Ground Troops' (PASGT) geometry) was used. The head model has previously been validated against several impact tests on cadavers. The helmet model was validated against data from shooting tests. Focus was aimed on getting a realistic response of the coupling between the helmet and the head and not on modeling the helmet in detail. The studied data from the FE simulations were stress in the cranial bone, strain in the brain tissue, pressure in the brain, change in rotational velocity and translational and rotational acceleration. A parametric study was performed to see the influence of a variation in helmet shell stiffness on the outputs from the model. The effect of different impact angles was also studied. Dynamic helmet shell deflections larger than the initial distance between the shell and the skull should be avoided in order to protect the head from the most injurious threat levels. It is more likely that a fracture of the skull bone occurs if the inside of the helmet shell strikes the skull. Oblique ballistic impacts may in some cases cause higher strains in the brain tissue than pure radial ones. r (S. Kleiven).
The Protective Performance of Modern Motorcycle Helmets Under Oblique Impacts
Annals of Biomedical Engineering
Motorcyclists are at high risk of head injuries, including skull fractures, focal brain injuries, intracranial bleeding and diffuse brain injuries. New helmet technologies have been developed to mitigate head injuries in motorcycle collisions, but there is limited information on their performance under commonly occurring oblique impacts. We used an oblique impact method to assess the performance of seven modern motorcycle helmets at five impact locations. Four helmets were fitted with rotational management technologies: a low friction layer (MIPS), three-layer liner system (Flex) and dampers-connected liner system (ODS). Helmets were dropped onto a 45° anvil at 8 m/s at five locations. We determined peak translational and rotational accelerations (PTA and PRA), peak rotational velocity (PRV) and brain injury criteria (BrIC). In addition, we used a human head finite element model to predict strain distribution across the brain and in corpus callosum and sulci. We found that the impac...
2002
This paper presents a simulation model of absorption effects during helmet collision with a hard obstacle.It is based on a necessity to predict undesired consequences that may occur in case of helemet colision and impact with a hard obstacle. The primary aim of the paper is to determine real deformations during helmet collision with a hard obstacle by method of simulation of energy absorption effects and to establish a successfull model of optimum helmet design, from the aspect of engineering purposes, which corresponds to helmet behaviour in real conditions. Finite elements of the thin laminar shell type are used in helmet discretisation. Boundary conditions and loads are applied in such a way to simulate impact in the most realistic way.
Statistical studies showed that the chin bar of full-face helmets is the region with the highest number of impacts. In an Australian research fifty percent of severe impacts took place to the front of helmet and forty percent of these resulted in Basilar Skull Fracture (BSF). There are two standards, which include some criteria for helmet’s chin bar, the first one is Snell M2005 and the second one is ECE 22.05. These standards have developed some methods for testing the chin bar in order to protect the head from facial impact during motorcycles accidents, but it seems that the standards have to consider head and neck injuries simultaneously, in order to prepare reasonable criteria for chin bar design. This work has utilized finite element method in order to compare the Snell M2005 and ECE 22.05 criteria for chin bar design with respect to the injuries at the base of the skull. In the first step, the helmet model has been used individually in order to simulate the chin bar test for b...
Journal of Safety Engineering, 2015
This report describes the results of a research project focused on helmet protection under impact of head to ground, and impact of an object to head. Three kinds of helmets were considered: construction, motorcycle and bicycle helmets. The goal of this project is to check the amount of stress absorbed by the skull and brain during the impact, as well as evaluate the maximum capacity of helmet protection. The material used for each helmet was the most common material in the current market, in order to make the results more realistic. The analysis consists of dynamic simulation of an impact in the helmet using Finite Element Analysis (FEA). First, the models were meshed using Hypermesh. After the modeling phase, analyses were made using ABAQUS (a computer aided engineering program) that shows the stresses and displacements experienced by the whole system: helmet, skull and brain. The results obtained from the analysis were displayed on charts that show the effect of the helmet based on different boundary conditions such as object height for the hard hat, and the rider speed for the bicycle and motorcycle helmets.
Finite element modelling of helmeted head impact under frontal loading
Sadhana, 2007
Finite element models of the head and helmet were used to study contact forces during frontal impact of the head with a rigid surface. The finite element model of the head consists of skin, skull, cerebro-spinal fluid (CSF), brain, tentorium and falx. The finite element model of the helmet consists of shell and foam liner. The foam is taken as elasto-plastic, the brain is assumed to be viscoelastic and all other components are taken as elastic. The contact forces and coup pressures with helmet on the head are much lower than in the absence of the helmet. A parametric study was performed to investigate the effect of liner thickness and density on the contact forces, pressures and energy absorption during impact. For 4 ms −1 velocity, expanded poly styrene (EPS) foam of density 24 kg m −3 gave the lowest contact forces and for the velocities considered, thickness of the foam did not affect the contact forces.